Heating RO water

[dot]

Here's the situation:

We are planning to build a "conservatory" (for orchid growing now, and later for anything whoever has this house after us). We've looked into using our well water -- too high in calcium and iron, bringing in water from our pond -- too expensive, and now we are thinking about an RO system. Likely this system would be in our basement with a hookup to the conservatory. In our basement, the water would be too cool to use directly.

So we need to heat it some way. But our heating/plumbing guy says he cannot find an appropriate heater because of the caustic nature of pure water.

How has anyone else solved this problem?